John Franklin McGraw of Linden, North Carolina, is shown in this booking photo provided by the Cumberland County Sheriff's Office in Fayetteville, North Carolina, March 10, 2016.
Cumberland County Sheriff's Office/Handout via Reuters

The release said the assault victim was being escorted out of Crown Coliseum after disrupting the rally, and deputies had their eyes on the stairs when the assault happened.

In an email in response to a question about the assault, Trump campaign spokeswoman Hope Hicks said only that "we are not involved."

The man who was punched, Rakeem Jones, told The Associated Press that he and others went to the event as observers, not protesters. He says someone swore at one of their group, and by the time they tried to object, the police were escorting him out.

"It was like, wow, I got hit while the police are escorting me out. ... The police watched me get hit," he said.

He said his right eye is swollen and bruised.

Rakeem Jones lies on the ground while being removed by deputies from a Donald Trump rally in Fayetteville, North Carolina, March 9, 2016, in a still image from video provided by Ronnie Rouse March 10, 2016.
Ronnie C/Handout via Reuters

Confrontations between protesters, Trump supporters and police have become standard at Trump rallies across the country. And Trump has incorporated reactions to them into his usual stump speech.

Audiences are usually told ahead of rallies in an announcement not to harm protesters - and instead attract authorities' attention by chanting, "Trump! Trump! Trump!"